Automotive regenerative braking systems having storage assemblies employing metal springs are well known. Such systems have been manually operated to effect vehicle braking by converting vehicle motion energy (kinetic energy) into resiliently stored potential energy and manually operated to effect vehicle acceleration with the stored energy. The storage assemblies employing metal springs have been unduly bulky and/or heavy. Further, the amount of braking and driving torque provided by such storage assemblies has not been readily controllable. Still further, the controls for such devices have not readily provided for an automatic or smooth transition from regenerative braking and driving to regular wheel braking and prime mover driving.